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Earthquake Detector 

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Earthquake Detector 

Written By: Andrea 


plastic board (1) 
crooked plastic lever (1) 
bearing (2) 
Washers (2) 


An earthquake detector can be a useful home safety device because it alerts you to a quake 
some seconds before it happens. During an earthquake two kinds of waves are emitted from 
the centre: a small wave and a dangerous wave. The small wave is faster, so it is the first 
sign of the event if your house is located some kilometres away from the centre. 

An earthquake detector could also work in combination with other devices, such as a gas 

This device consists of a highly sensitive lever which is hooked to a spring. A weight is fixed 
at the end of the lever by an M8 screw. The lever should resonate with a frequency of about 
2 HZ. When the sensor shakes, an M3 screw fixed on the lever will touch the horizontal 
spring, and it will close a delay-off circuit which drives a piezoelectric buzzer. 

Construction drawing (pdf) 

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Earthquake Detector 

Electric circuit 

Step 1 — Earthquake Detector 

• Make the holes on the plastic 
board: 3 millimetres in diameter for 
the springs' anchor bolts (affix 
three M3 screws); 4 millimetres in 
diameter for the lever fulcrum (affix 
an M4 screw). 

• Make the bearing housing on both 
sides of the lever: drill 8 
millimetres in diameter on full 
depth; 9 millimetres in diameter on 
the sides. 

• Make the hole for the spring anchor 
bolt (M3 screw) on the lever. 

• Make the hole for the switch screw 
on the lever. 

• Affix an M8 screw with a weight (I 
used some screw nuts) at the end 
of the lever. 

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Earthquake Detector 

Step 2 


• Affix the springs and the lever on 
the board using self-lock screw 

• Put washers on both bearings (I 
used brass washers). 

■ Do not overtighten the M4 
screw nut on the bearings; 
otherwise the lever will not be 

• Connect a wire to the static anchor 
bolt of the lever spring. 

• Connect the moving anchor bolt of 
the lever spring to the switch screw 
(you'll see a red wire jumper). 

• Connect a wire to the horizontal 

• Connect the free ends of the wires 
to a delay-off bell circuit. 

It works quite fine, though some details need to be fixed. 

This document was last generated on 201 2-1 1 -03 03:48:59 AM. 

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